/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.aop.aspectj;

import java.lang.reflect.InvocationTargetException;

import org.springframework.aop.framework.AopConfigException;
import org.springframework.core.Ordered;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;

/**
 * Implementation of {@link AspectInstanceFactory} that creates a new instance
 * of the specified aspect class for every {@link #getAspectInstance()} call.
 *
 * @author Juergen Hoeller
 * @since 2.0.4
 */
public class SimpleAspectInstanceFactory implements AspectInstanceFactory {

    private final Class<?> aspectClass;


    /**
     * Create a new SimpleAspectInstanceFactory for the given aspect class.
     *
     * @param aspectClass the aspect class
     */
    public SimpleAspectInstanceFactory(Class<?> aspectClass) {
        Assert.notNull(aspectClass, "Aspect class must not be null");
        this.aspectClass = aspectClass;
    }

    /**
     * Return the specified aspect class (never {@code null}).
     */
    public final Class<?> getAspectClass() {
        return this.aspectClass;
    }


    @Override
    public final Object getAspectInstance() {
        try {
            return ReflectionUtils.accessibleConstructor(this.aspectClass).newInstance();
        } catch (NoSuchMethodException ex) {
            throw new AopConfigException(
                    "No default constructor on aspect class: " + this.aspectClass.getName(), ex);
        } catch (InstantiationException ex) {
            throw new AopConfigException(
                    "Unable to instantiate aspect class: " + this.aspectClass.getName(), ex);
        } catch (IllegalAccessException ex) {
            throw new AopConfigException(
                    "Could not access aspect constructor: " + this.aspectClass.getName(), ex);
        } catch (InvocationTargetException ex) {
            throw new AopConfigException(
                    "Failed to invoke aspect constructor: " + this.aspectClass.getName(), ex.getTargetException());
        }
    }

    @Override
    @Nullable
    public ClassLoader getAspectClassLoader() {
        return this.aspectClass.getClassLoader();
    }

    /**
     * Determine the order for this factory's aspect instance,
     * either an instance-specific order expressed through implementing
     * the {@link org.springframework.core.Ordered} interface,
     * or a fallback order.
     *
     * @see org.springframework.core.Ordered
     * @see #getOrderForAspectClass
     */
    @Override
    public int getOrder() {
        return getOrderForAspectClass(this.aspectClass);
    }

    /**
     * Determine a fallback order for the case that the aspect instance
     * does not express an instance-specific order through implementing
     * the {@link org.springframework.core.Ordered} interface.
     * <p>The default implementation simply returns {@code Ordered.LOWEST_PRECEDENCE}.
     *
     * @param aspectClass the aspect class
     */
    protected int getOrderForAspectClass(Class<?> aspectClass) {
        return Ordered.LOWEST_PRECEDENCE;
    }

}
